First read: previewing tonight's NBC News-YouTube Democratic debate

CHARLESTON, SC — It's such a busy Sunday in politics — tonight's Democratic NBC/YouTube debate, the results from our new NBC/WSJ poll showing Hillary Clinton with a 25-point national lead over Bernie Sanders, and so many candidates on the Sunday shows — we bring you a rare weekend edition of our morning column.

And the point we want to make is how the Democratic presidential contest, which is neck-and-neck in Iowa, has turned into a true fight over the heart and soul of the Democratic Party. Do Democrats go with the candidate essentially running on continuity with President Obama (Clinton), or do they back the candidate promising revolution (Sanders)? Should their nominee be another Clinton? Or should it be a self-avowed democratic socialist who hasn't been a member of the party until now?

We've spent so much time looking at the establishment-vs.-insurgent divide inside the Republican Party, but don't dismiss the equally compelling fight within the Democratic Party over where it should be entering Year 8 of the Obama presidency. NBC's Perry Bacon puts it well: It's a contest between the dreamers (Sanders and his supporters) and the doers (Clinton and her supporters).

Sanders wins among the Democrats who want change, Clinton wins among those who want experience and a tested candidate

Our new NBC/WSJ poll results, released just an hour ago, also demonstrate this party split. While Clinton leads Sanders by 25 points nationally, 59%-34%, the Vermont senator bests Clinton among the four-in-10 Democratic voters who prefer a presidential candidate who brings change to current policies, 52%-39%. Yet among the more than half of Democrats who instead want experience and a tested candidate, Clinton beats Sanders, 77%-19%. Overall, 61% of all voters -- Democratic, Republican and independent -- want change, while 36% prefer experience. Here's one more finding from our new NBC/WSJ poll: Sanders outperforms Clinton in a hypothetical matchup against Donald Trump, though both are beating him:

Clinton 51%, Trump 41%
Sanders 54%, Trump 39%

Three questions heading into tonight's debate

Tonight's Democratic debate -- their first one of 2016 and the last one until the Feb. 1 Iowa caucuses -- takes place at 9:00 pm ET at the Gaillard Center here in Charleston. And it's moderated by NBC's Lester Holt and Andrea Mitchell. Our three questions:

Does the pressure bring up the best -- or worst -- in Clinton? NBC/WSJ co-pollster Peter Hart (D) remarked last summer that Clinton is a subpar candidate when she's the overwhelming frontrunner, but that she's much, much better when her back is against the wall. We'll see if that pattern continues with a closer-than-expected race in all-important Iowa. "I always thought that this would be close," Clinton said on "Meet the Press" this morning, per NBC's Monica Alba.

Can Sanders handle the heat coming his way? The Clinton campaign has spent the last week hammering Sanders on the issues of guns and health care. And Sanders last night announced that he was cleaning up one problematic area -- his 2005 vote giving immunity to gun manufacturers -- by supporting a bill to amend that 2005 legislation. "We have rethought," Sanders said on "Meet the Press" this morning. "There's a bill apparently being introduced, I like that bill, it makes some good changes, and we will be supportive of it."

Can O'Malley make a good impression? This is a question we've had for Martin O'Malley before the last three Dem debates, and the former Maryland governor -- who is at 2% in the NBC/WSJ poll -- is still looking for a break-out performance before time runs out.

See photos from the most recent Democratic debate below:

17PHOTOS

12/19/2015: Third Democratic Debate

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First read: previewing tonight's NBC News-YouTube Democratic debate

MANCHESTER, NH - DECEMBER 19: Democratic president candidate Bernie Sanders takes the stage at the democratic debate at Saint Anselm College December 19, 2015 in Manchester, New Hampshire. This is the third Democratic debate featuring Democratic candidates Hillary Clinton, Bernie Sanders and Martin O'Malley. (Photo by Andrew Burton/Getty Images)

Hillary Clinton, former Secretary of State and 2016 Democratic presidential candidate, waves as she arrives to the Democratic presidential candidate debate at Saint Anselm College in Manchester, New Hampshire, U.S., on Saturday, Dec. 19, 2015. A Democratic presidential campaign that has looked tame compared to the one being waged by Republicans appears to be taking a sharp turn for the nasty as the three candidates participate in their third debate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Senator Bernie Sanders, an independent from Vermont and 2016 Democratic presidential candidate, arrives to the Democratic presidential candidate debate at Saint Anselm College in Manchester, New Hampshire, U.S., on Saturday, Dec. 19, 2015. A Democratic presidential campaign that has looked tame compared to the one being waged by Republicans appears to be taking a sharp turn for the nasty as the three candidates participate in their third debate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Senator Bernie Sanders, an independent from Vermont and 2016 Democratic presidential candidate, speaks during the Democratic presidential candidate debate at Saint Anselm College in Manchester, New Hampshire, U.S., on Saturday, Dec. 19, 2015. A Democratic presidential campaign that has looked tame compared to the one being waged by Republicans appears to be taking a sharp turn for the nasty as the three candidates participate in their third debate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Hillary Clinton, former Secretary of State and 2016 Democratic presidential candidate, smiles after walking on stage following a break in the Democratic presidential candidate debate at Saint Anselm College in Manchester, New Hampshire, U.S., on Saturday, Dec. 19, 2015. A Democratic presidential campaign that has looked tame compared to the one being waged by Republicans appears to be taking a sharp turn for the nasty as the three candidates participate in their third debate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Senator Bernie Sanders, an independent from Vermont and 2016 Democratic presidential candidate, left, and Hillary Clinton, former Secretary of State and 2016 Democratic presidential candidate, share a laugh during a break in the Democratic presidential candidate debate at Saint Anselm College in Manchester, New Hampshire, U.S., on Saturday, Dec. 19, 2015. A Democratic presidential campaign that has looked tame compared to the one being waged by Republicans appears to be taking a sharp turn for the nasty as the three candidates participate in their third debate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Senator Bernie Sanders, an independent from Vermont and 2016 Democratic presidential candidate, left, and Hillary Clinton, former Secretary of State and 2016 Democratic presidential candidate, share a laugh during a break in the Democratic presidential candidate debate at Saint Anselm College in Manchester, New Hampshire, U.S., on Saturday, Dec. 19, 2015. A Democratic presidential campaign that has looked tame compared to the one being waged by Republicans appears to be taking a sharp turn for the nasty as the three candidates participate in their third debate. Photographer: Andrew Harrer/Bloomberg via Getty Images

MANCHESTER, NH - DECEMBER 19: Democratic president candidate Bernie Sanders waits as Hillary Clinton walks on stage at Saint Anselm College December 19, 2015 in Manchester, New Hampshire. This is the third Democratic debate featuring Democratic candidates Hillary Clinton, Bernie Sanders and Martin O'Malley. (Photo by Andrew Burton/Getty Images)

MANCHESTER, NH - DECEMBER 19: Democratic president candidate Bernie Sanders speaks at the debate at Saint Anselm College December 19, 2015 in Manchester, New Hampshire. This is the third Democratic debate featuring Democratic candidates Hillary Clinton, Bernie Sanders and Martin O'Malley. (Photo by Andrew Burton/Getty Images)

2016 Democratic presidential candidates Senator Bernie Sanders, an independent from Vermont, from left, Hillary Clinton, former Secretary of State, and Martin O'Malley, former governor of Maryland, participate in the Democratic presidential candidate debate at Saint Anselm College in Manchester, New Hampshire, U.S., on Saturday, Dec. 19, 2015. A Democratic presidential campaign that has looked tame compared to the one being waged by Republicans appears to be taking a sharp turn for the nasty as the three candidates participate in their third debate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Martin O'Malley, former governor of Maryland and 2016 Democratic presidential candidate, speaks during the Democratic presidential candidate debate at Saint Anselm College in Manchester, New Hampshire, U.S., on Saturday, Dec. 19, 2015. A Democratic presidential campaign that has looked tame compared to the one being waged by Republicans appears to be taking a sharp turn for the nasty as the three candidates participate in their third debate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Martin O'Malley, former governor of Maryland and 2016 Democratic presidential candidate, right, speaks as Hillary Clinton, former Secretary of State and 2016 Democratic presidential candidate, listens during the Democratic presidential candidate debate at Saint Anselm College in Manchester, New Hampshire, U.S., on Saturday, Dec. 19, 2015. A Democratic presidential campaign that has looked tame compared to the one being waged by Republicans appears to be taking a sharp turn for the nasty as the three candidates participate in their third debate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Finally, while the attention is on the Democratic race today, the war of words between Donald Trump and Ted Cruz continues. On Fox this morning, Cruz said it was "curious" why Trump is so outraged over the "New York values" remark -- given that Trump talked about New York values on abortion in a 1999 "Meet the Press" interview. Meanwhile, on ABC, Trump called Cruz "a nasty guy." "He's a nasty guy. Nobody likes him. Nobody in Congress likes him. Nobody likes him anywhere once they get to know him. He's a very -- he's got an edge that's not good. You can't make deals with people like that and it's not a good thing. It's not a good thing for the country. Very nasty guy." Bottom line: This is only good news for Marco Rubio and the other establishment types. Speaking of Rubio, here was on "Meet" this morning whacking Cruz: "He raises money in New York and then criticizes New York values."

On the trail

Beyond tonight's Dem debate, Ted Cruz campaigns in New Hampshire... Chris Christie and Rand Paul are in Iowa... And Carly Fiorina and Rick Santorum address the South Carolina Tea Party convention.